Method of and material for protecting and conditioning metal surfaces



Patented June 21, 1949 METHOD OF AND MAT ING AND CONDITI FACES ERIAL FORPROTECT- ONING METAL SUR- Eugene Snyder, Philadelphia, Pa., assignor toAmerican Chemical Paint Company, Ambler, Pa., a corporation of DelawareNo Drawing. Application December 13,1945,

Serial No. 634,891 I 7 Claims. (01. 148--6.15)

This invention relates to the art of finishing metal surfaces and isparticularly concerned with that type of metal finishing which includesapplication to the surface of an organic coating such as paint, varnish,lacquer, japan or the like for either decorative or protective purposes.The invention is particularly applicable to the finishing of surfaces ofiron, zinc, aluminum and of ironbase, zinc-base and aluminum basealloys.

The invention has for its purpose the attainment of the followingobjectives:

(a) The provision of a method and material for affording temporaryprotection to the surface against rusting, corrosion or contamination byatmospheric influences after the completion, or during the latterstages,of mechanical operations to which the metal objects may be subjected.

(b) The provision of a method and material for rendering anypre-existing light deposits of corrosion products or corrosionstimulative substances entirely innocuous either to the surface of themetal itself or to any subsequently applied organic coating.

The provision of a method and material for coating or conditioning thesurface of the metal for the reception of the final organic finish so asto assure even retention, maximum adhesion and maximum life of the paintfilm either in use or during storage.

(d) The provision of a method and material for finishing metal surfacesin which the chemical reactions involved in conditioning the metal forthe reception of the final paint film continue while the metal objectsare in storage, in transit between diiferent locations within a plant orbetween dilferent plants or even while they are being subjected tomachining or other mechanical operations.

(e) The provision of a method and material for use in conditioning metalsurfaces for the reception of a final finish of paint and the like whichmakes vapor degreasing a safe and convenient step in the finishingprocess, in which connection it should be noted that vapor degreasinghas not hitherto been entirely safe and practical where the parts are tobe painted because of the deleterious effects of traces of hydrochloricacid which are often present in the vapors of the chlorinated solventswhich are often encountered during the degreasing operation.

(I) The provision of a method and material I or use in the finishing ofmetal surfaces by means of which the amount of space and labor requiredas well as the degree of supervision necessary are greatly reduced andin general to provide a 2 method and material for use in the finishingof metal surfaces which is exceptionally simple, con-' venient andeffective.

How the foregoing objectives to ether with any others which may appearhereinafter or are incident to my invention are attained will appeartimately incorporated orthophosphoric acid in an .amount small comparedwith theamount of oily matter, together with such amounts of solvents,emulsifying agents, etc. as are necessary to obtain intimateincorporation or mutual solution of the oily matter with the acid.

(2) Allowing adhering material to remain upon the surface, not onlyuntil volatile solvents,

water, etc. have largely evaporated but also until the acid has had anopportunity to react with the metal to a substantial extent. The timeneces-' sary for substantial reaction varies, of course, like allchemical reactions, with the temperature. It varies also with theviscosity of the oily part used, the length of time the solvents take toevaporate, etc. At room temperature (average living ternperature) orbelow I prefer to allow an hour or more to pass before proceeding to thenext step since experiment has shown that this interval is necessary toassure optimum results. At elevated temperatures as little as fiveminutes or less may suffice.

Longer periods of drying of the composition of step 1 above do no harm.In fact, the materials are designed, as above indicated, to react withdeleterious materials originally upon the surfaces to render theminnocuous, to act chemically upon the surface, coating it orconditioning it for the reception of paint, and, finally to affordtemporary protection against rust or corrosion during fabrication,storage, or shipping of the partly finished work. The chemical actionsinvolved may not be completed for a long time, perhaps for days.Usually, however, the beneficial effects of the chemical action will befully realized within the time indicated above, depending on thetemperature.

(3) Removing the oil, fat, wax or similar substances from the surfacewithout removing the chemical reaction products of the-material ofstep 1. This may be accomplished by washing the surface with a suitableorganic solvent either greasr using ethylene trichloride.

'3 as such or in the form A very suitable method consists in condensingthe vapor of the solvent upon the surface. This method, which may or maynot be combined with simple washing in hot or cold solvent, is commonlyknown as "vapor degreasing." To avoid fire hazard it is usually carriedout with chlorinated solvents such as trichlorethylene,perchlorethylene, carbon tetrachloride, etc.

This step of washing away the oily" part of I the coating is preferablycarried out just prior to cautions are necessary in this step.

It will be found, as stated above, that the surface at this stage isexcellent for the reception and retention of the paint.

By way of specific example I wish to cite the following.

A solution was prepared in accordance with the following formula:

Foams No. 1

Degras -pounds 3.000 Mineral spirits gallons 0.35 Pine il do 0.13Monobutyi ether of ethylene glycol -do 0.13 85% phosphoric acid pounds0.31

On thorough mixing the above composition made a clear brown solution. onstanding, a little waxy material from the degras precipitated. Nodifilculty arose from the presence of this precipitate.

The metal articles to be treated were dipped for a short time into thesolution of Formula No. 1, following which they were allowed to drainuntil no more of the composition dripped from them. and were then packedinto boxes for shipment to another point for some mechanical treatment.The objects were in storage or en route for from two days to one week.depending upon the conditions obtaining at the time either in the plantsor with the carriers.

After unpacking at the point of destination the objects were thoroughlydegreased in a vapor de- They were then subjected to an operationentirely foreign to the finishing operation, following which they weresprayed with a conventional nitrocellulose lacquer formulated inaccordance with a standard specification. My improved method andmaterial re-' sulted in an excellent finish which met all specificationsfor adhesion of the lacquer, better than of an aqueous emulsion.

of cold-rolled annealed steel suitable for the manufacture of smallstampings were treated at the mill with the composition of FormulaNo. 1. The material was applied to the blanks with an automatic paintspray gun, after which the blanks were packed and shipped to the factorywhere they were cut and stamped in a punch press into the completelyformed articles. The articles were then washed with hottetrachlorethyene, finally vapor degreased in the same solvent. andpainted with two coats of a paint system of which each coat was appliedby dipping and was force dried in an air oven. The paint system usedincluded a primer based on alkyd resin and a top coat formulated withurea-formaldehyde resins.

Formula No. 1 above is formulated with degras as the oily" part whichremains on. the metal surface after the solvents have evaporated. Thefilm left on the surface includes the reaction products of thephosphoric acid and the metal, of

the degras and the metal, and residual degras itself. It is extremelyadherent and protective and even affords surface protection under severeconditions'for relatively long periods of time. Degras is an example ofso-called polar" compounds which impart to oily films relatively greatcorrosion-protective power.

Examples of compositions containing mixtures of degras and minor amountsof non-polar oily" parts are the following:

Foams No. 2

Degras pounds 3.00 Boya bean oil gallons 0.18 Mineral pir do 0.18 Butylalcohol o 0.14 Monobutyl ether of ethylene glycol -do- 0.14 85%Phosphoricacld pounds 0.25

Foams No. 3

Degras pounds 2.30 Light mineral oil gallons- 0.14 Butyl alcohol do 0.22Xylol do 0.17 Carbon tetrachloride do 0.17 85% Phosphoric acid pound0.24

The above formulas all furnish consolute mix-' tures of the acid and theoily part in blends of solvents serving to bring all the ingredientsinto solution. Two further formulas are given below whic exemplifyintimate admixtures of acid and degras which 'are not consolute butwhich exist as emulsions. Such emulsions are suitable for carrying outmy improved finishing process provided they are sumciently stable andare thoroughly agitated before being applied to the metal surfaces, and

provided the composition spreads evenly over the surfaces, whichsurfaces may be somewhat greasy required life in accelerated testing,etc. In short the process was a considerable improvement over previouspractice which had involved covering the objects with a light slushingoil during shipment. Furthermore. the objections heretofore resultingfrom contamination during the various handling 7 operations to which theobjects were subiected were completely overcome because the objectsarrived at the final plant in a condition which required no special rustremoval before they could bepainted. In this way a great deal of extraspace and labor as well as supervision were rendered unnecessary.

In another application of'my invention, blanks when the composition isapplied.

Foiunms No. 4

Part A 7 Pounds Degras 3.333 Sorbitan mono-oleate polyalkylenederivative 0.417

Part B Gallons Water 4 0.97 Polyglycol ether derivative 0.03 Phosphoricacid 0.02 The degras is melted andthoroughly mixed with the sorbitanmono+oleate poiyalkylene derivative,

Foams No.

Part A Degras pounds 4.1 A sorbitan mono-oleate polyalkylene derivative"do 0.25 Xylol gallons 0.50

Melt degras, add the other ingredients and mix thoroughly.

Part B Gallons Water 0.97 A polyglycol ether derivative 0.01 85%phosphoric acid 0.03

Mix thoroughly. Pour Part A into Part B with violent stirring.

Formula No. 5 may be used as is, or may be thinned as desired withxylol.

The formulas given above are illustrative and are not meant to belimiting in scope. A suitable admixture'for carrying out my improvedfinishing process must merely conform to the following description 1. Itmust contain a substantial quantityof water-insoluble organic materialthe totality of which, if more than one is present, has an oily, greasy,or waxy consistency the principal component of which should be degras.

2. The "oily portion just described must be intimately admixed withphosphoric acid. The amount of phosphoric acid present in the admixture,calculated as pure HaPO4, should be between about 1 and 15% by weight ofthe oily part of the admixture, depending upon the amount of chemicalaction On the metal surface which is desired, and upon the reactivity ofthe metal. More acid than the upper limit set above yields irregular andrough reaction products which are likely to be injurious to the finishobtained.

3. Intimate admixture of the acid and the "oily portion may be obtainedby using suitable mixtures of solvents to obtain homogeneous solutions,or by emulsifying together the acid and the oily part, or by othersuitable means. Naturally, solvents will be selected which arereasonably stable to phosphoric acid and which have no deleteriouseffect on the metal surface to be finished.

Although the examples given above exemplify my process of finishing asit is carried out on steel, it is to be understood that it is alsouseful on aluminum and its alloys and on zinc or its alloys.

I claim:

1. A material for use in treating a surface of metal from the groupconsisting of iron, zinc, aluminum and of iron-base, zinc-base andaluminum-base alloys, the principal active ingredients of which materialconsist of an intimate admixture of degras and orthophosphoric acidtogether with a liquid vehicle for said admixture, the quantity oforthophosphoric acid being from 1 to by weight of the degras and thequantity of the vehicle being sufficient to obtain intimateincorporation of the degras with the acid.

2. The material of claim 1 in which said vehicle consists of organicsolvents rendering the whole consolute.

3. The material of claim 1 in which the said admixture is formulated asan emulsion including water.

4. A method of finishing a surface of metal from the group consisting ofiron, zinc, aluminum and of iron-base. zinc-base and aluminum-basealloys, which method consists in applying to the surface a material theprincipal active ingredients of which consist of an oily component,including degras as the principal oily constituent, intimately admixedwith orthophosphoric acid in which the amount of acid, calculated aspure H3PO4 is between 1 and 15% by weight of the oily component;allowing adhering material to remain upon the surface until thephosphoric acid and the degras have reacted with the metal to asubstantial extent; removing the oily component by washing the surfacewith an organic solvent; and applying to the washed surface a finalcoating of paint, varnish, lacquer, japan or the I like.

5. The method of claim 4 in which the material contains a volatilesolvent system which renders it consolute.

6. The method of claim 4 in which the material is formed as an emulsionincluding water.

7. The method of claim 4 in which at least one hour elapses between theapplication of the material and its removal and in which the surface isA maintained at a temperature not higher than average living-roomtemperature during the elapsed interval.

EUGENE SNYDER.

REFERENCES CITED The following referemces are of record in the file ofthis patent:

UNITED STATES PATENTS c

